In fact, the supplements appear to lower risk of death from any cause, according to an analysis of 18 previously published studies, which is featured in the September 10 issue of Archives of Internal Medicine.

Past studies have suggested that deficiencies in vitamin D might be associated with a higher risk of death from cancer, heart disease and diabetes — illnesses that account for 60 percent to 70 percent of deaths in high-income nations, according to background information in the article.

“If the associations made between vitamin D and these conditions were consistent, then interventions effectively strengthening vitamin D status should result in reduced total mortality,” the authors wrote.

Dr. Philippe Autier of the International Agency for Research on Cancer in Lyon, France, and Sara Gandini, Ph.D., of the European Institute of Oncology in Milano, Italy, studied randomized controlled trials of vitamin D supplements published before November 2006.

The studies analyzed by the two included a total of 57,311 participants and evaluated doses of vitamin D ranging from 300 to 2,000 international units, with an average dose of 528 IU.

Over an average follow-up period of 5.7 years, 4,777 of the participants died. Individuals who took vitamin D had a 7 percent lower risk of death than those who did not. In the nine trials that collected blood samples, those who took supplements had an average 1.4- to 5.2-fold higher blood level of vitamin D than those who did not.

“Mechanisms by which vitamin D supplementation would decrease all-cause mortality are not clear,” the authors said.

It is believed that vitamin D may inhibit some mechanisms by which cancer cells proliferate, or it may boost the function of blood vessels or the immune system, the two said.

The authors said more studies are needed, especially placebo-based trials on individuals age 50 and older.